Systems and leads with a radially segmented electrode array and methods of manufacture

ABSTRACT

A method of making a lead for a stimulation device includes forming at least one pre-electrode in the shape of a ring, the at least one pre-electrode comprises at least two thin-walled portions separated by at least two thick-walled portions; disposing the at least one pre-electrode near a distal end of a lead body; joining at least one conductor to each thick-walled portion of the at least one pre-electrode; and grinding the lead body and the at least one pre-electrode to remove the thin-walled portions of the at least one pre-electrode to form segmented electrodes from the thick-walled portions of the at least one pre-electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 13/776,143 filed on Feb. 25, 2013 which is a divisional of U.S.patent application Ser. No. 12/498,650 filed on Jul. 7, 2009, whichissued as U.S. Pat. No. 8,887,387, both of which are incorporated hereinby reference.

FIELD

The invention is directed to methods for brain stimulation includingdeep brain stimulation. In addition, the invention is directed tomethods for manufacturing a lead for brain stimulation having aplurality of segmented electrodes.

BACKGROUND

Deep brain stimulation can be useful for treating a variety ofconditions including, for example, Parkinson's disease, dystonia,essential tremor, chronic pain, Huntington's Disease, levodopa-induceddyskinesias and rigidity, bradykinesia, epilepsy and seizures, eatingdisorders, and mood disorders. Typically, a lead with a stimulatingelectrode at or near a tip of the lead provides the stimulation totarget neurons in the brain. Magnetic resonance imaging (MM) orcomputerized tomography (CT) scans can provide a starting point fordetermining where the stimulating electrode should be positioned toprovide the desired stimulus to the target neurons.

Upon insertion, current is introduced along the length of the lead tostimulate target neurons in the brain. This stimulation is provided byelectrodes, typically in the form of rings, disposed on the lead. Thecurrent projects from each electrode equally in every direction at anygiven length along the axis of the lead. Because of the shape of theelectrodes, radial selectivity of the current is minimal. This resultsin the unwanted stimulation of neighboring neural tissue, undesired sideeffects and an increased duration of time for the proper therapeuticeffect to be obtained.

Studies have shown that current methods of manufacture produce deepbrain stimulation leads that are unreliable and prone to failure. Onestudy shows that lead breakage rates for some lead products are reportedanywhere from 6.8-12.4%, and that the breakage occurs on average from260-390 days. Thus in many cases, revision surgery is needed within ashort period of time. This revision surgery is physically, mentally andfinancially taxing on the patient.

BRIEF SUMMARY

In some embodiments, a method of making a lead for a stimulation deviceincludes forming at least one pre-electrode in the shape of a ring, theat least one pre-electrode comprises at least two thin-walled portionsseparated by at least two thick-walled portions; disposing the at leastone pre-electrode near a distal end of a lead body, joining at least oneconductor to each thick-walled portion of the at least onepre-electrode; and grinding the lead body and the at least onepre-electrode to remove the thin-walled portions of the at least onepre-electrode to form a plurality of segmented electrodes from thethick-walled portions of the at least one pre-electrode.

In some embodiments, a method of making a lead for a stimulation deviceincludes coupling a plurality of electrodes to a temporary plate;joining individual conductors to each of the plurality of electrodes;forming the temporary plate into a cylinder with the conductorsextending through a lumen of the cylinder; filling the lumen of thecylinder with an insulative material to create a lead assembly; andremoving the temporary plate having the plurality of electrodes exposed.

In some embodiments, a method of making a lead for a stimulation deviceincludes disposing a plurality of electrodes in a mold and overmoldingin a flexible carrier; removing the flexible carrier and electrodes fromthe mold; joining conductors to the plurality of electrodes to form acarrier; shaping the carrier into a substantially cylindrical shape; andjoining the carrier to a lead body.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

For a better understanding of the present invention, reference will bemade to the following Detailed Description, which is to be read inassociation with the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view of one embodiment of a portion ofa lead having a plurality of segmented electrodes, according to theinvention;

FIG. 2 is a schematic perspective view of another embodiment of aportion of a lead having a plurality of segmented electrodes arranged ina staggered orientation, according to the invention;

FIG. 3A is a schematic perspective view of a third embodiment of aportion of a lead having a plurality of segmented electrodes, accordingto the invention;

FIG. 3B is a schematic perspective view of a fourth embodiment of aportion of a lead having a plurality of segmented electrodes, accordingto the invention;

FIG. 4 is a schematic diagram of radial current steering along variouselectrode levels along the length of a lead, according to the invention;

FIG. 5 is a perspective view of a portion of a lead having conductorscables exposed at the distal end, according to the invention;

FIG. 6 is a schematic cross-sectional view of a pre-electrode having twothin-walled portions separated by two thick-walled portions, accordingto the invention;

FIG. 7 is a schematic cross-sectional view of the pre-electrode of FIG.6 after the thin-walled portions have been removed to create twosegmented electrodes, according to the invention;

FIG. 8 is a schematic cross-sectional view of a pre-electrode havingthree thin-walled portions separated by three thick-walled portions,according to the invention;

FIG. 9 is a schematic cross-sectional view of the pre-electrode of FIG.8 after the thin-walled portions have been removed to create threesegmented electrodes, according to the invention;

FIG. 10A is a schematic perspective view of a plurality of electrodescoupled to a plate, according to the invention;

FIG. 10B is a schematic perspective view of the plurality of electrodescoupled a plate after the plate has been formed into a cylinder,according to the invention;

FIG. 10C is a schematic perspective view of the cylinder of FIG. 10Bafter its lumen has been filled with an insulative material to create alead assembly, according to the invention;

FIG. 10D is a schematic perspective view of the cylinder of FIG. 10Cafter the plate has been removed, according to the invention;

FIG. 11A is a schematic cross-sectional view of one embodiment of anarray of electrodes positioned within a carrier mold, according to theinvention;

FIG. 11B is a schematic cross-sectional view of the carrier mold and thearray of electrodes of FIG. 11A after a carrier mold cover has beenplaced over the carrier mold, according to the invention;

FIG. 11C is a schematic cross-sectional view of the assembly of FIG. 11Bafter a carrier has been molded around the array of electrodes,according to the invention;

FIG. 11D is a schematic perspective view of an electrode overmolded in aliquid injection molding carrier, according to the invention; and

FIG. 12 is a schematic side view of one embodiment of a lead and astylet, according to the invention.

DETAILED DESCRIPTION

The present invention is directed to the area of devices and methods forbrain stimulation including deep brain stimulation. In addition, theinvention is directed to methods for manufacturing a lead for brainstimulation having a plurality of segmented electrodes.

A lead for deep brain stimulation may include stimulation electrodes,recording electrodes, or a combination of both. A practitioner maydetermine the position of the target neurons using the recordingelectrode(s) and then position the stimulation electrode(s) accordinglywithout removal of a recording lead and insertion of a stimulation lead.In some embodiments, the same electrodes can be used for both recordingand stimulation. In some embodiments, separate leads can be used; onewith recording electrodes which identify target neurons, and a secondlead with stimulation electrodes that replaces the first after targetneuron identification. A lead may include recording electrodes spacedaround the circumference of the lead to more precisely determine theposition of the target neurons. In at least some embodiments, the leadis rotatable so that the stimulation electrodes can be aligned with thetarget neurons after the neurons have been located using the recordingelectrodes.

Deep brain stimulation devices and leads are described in the art. See,for instance, U.S. Pat. No. 7,809,446 (“Devices and Methods For BrainStimulation”), U.S. Patent Application Publication No. 2010/0076535(“Leads With Non-Circular-Shaped Distal Ends For Brain StimulationSystems and Methods of Making and Using”), U.S. Patent ApplicationPublication 2007/0150036 A1 (“Stimulator Leads and Methods For LeadFabrication”), U.S. Patent Application Publication No. 2009/0276021(“Electrodes For Stimulation Leads and Methods of Manufacture and Use”),U.S. patent application Ser. No. 12/177,823 (“Lead With Transition andMethods of Manufacture and Use”), and U.S. Patent Application Ser. No.61/170,037 entitled “Deep Brain Stimulation Current Steering with SplitElectrodes.” Each of these references is incorporated herein byreference in its respective entirety.

FIG. 12 illustrates one embodiment of a device 1200 for brainstimulation. The device includes a lead 100, ring electrodes 120,segmented electrodes 130, and a stylet 1220 for assisting in insertionand positioning of the lead in the patient's brain. The stylet 1220 canbe made of a rigid material. Examples of suitable materials includetungsten, stainless steel, or plastic. The stylet 1220 may have a handle1230 to assist insertion into the lead, as well as rotation of thestylet and lead. A proximal end is coupled to, or coupleable to, acontrol unit.

In one example of operation, access to the desired position in the braincan be accomplished by drilling a hole in the patient's skull or craniumwith a cranial drill (commonly referred to as a burr), and coagulatingand incising the dura mater, or brain covering. The lead 100 can beinserted into the cranium and brain tissue with the assistance of thestylet 1220. The lead can be guided to the target location within thebrain using, for example, a stereotactic frame and a microdrive motorsystem. In some embodiments, the microdrive motor system can be fully orpartially automatic. The microdrive motor system may be configured toperform one or more the following actions (alone or in combination):rotate the lead, insert the lead, or retract the lead. In someembodiments, measurement devices coupled to the muscles or other tissuesstimulated by the target neurons or a unit responsive to the patient orclinician can be coupled to the control unit or microdrive motor system.The measurement device, user, or clinician can indicate a response bythe target muscles or other tissues to the stimulation or recordingelectrode(s) to further identify the target neurons and facilitatepositioning of the stimulation electrode(s). For example, if the targetneurons are directed to a muscle experiencing tremors, a measurementdevice can be used to observe the muscle and indicate changes in tremorfrequency or amplitude in response to stimulation of neurons.Alternatively, the patient or clinician may observe the muscle andprovide feedback.

The lead 100 for deep brain stimulation can include stimulationelectrodes, recording electrodes, or both. In at least some embodiments,the lead is rotatable so that the stimulation electrodes can be alignedwith the target neurons after the neurons have been located using therecording electrodes.

Stimulation electrodes may be disposed on the circumference of the leadto stimulate the target neurons. Stimulation electrodes may bering-shaped so that current projects from each electrode equally inevery direction at any given length along the axis of the lead. Toachieve current steering, segmented electrodes can be utilizedadditionally or alternatively. Though the following descriptiondiscusses stimulation electrodes, it will be understood that allconfigurations of the stimulation electrodes discussed may be utilizedin arranging recording electrodes as well.

FIG. 1 illustrates one embodiment of a lead 100 for brain stimulation.The device includes a lead body 110, one or more optional ringelectrodes 120, and a plurality of segmented electrodes 130. The leadbody 110 can be formed of a biocompatible, non-conducting material suchas, for example, a polymeric material. Suitable polymeric materialsinclude, but are not limited to, silicone, polyurethanes, polyethylene,polyureas, or polyurethane-ureas. In at least some instances, the leadmay be in contact with body tissue for extended periods of time. In atleast some embodiments, the lead has a cross-sectional diameter of nomore than 1.5 mm and may be in the range of 1 to 1.5 mm in at least someembodiments, the lead has a length of at least 10 cm and the length ofthe lead may be in the range of 25 to 70 cm.

In at least some embodiments, stimulation electrodes may be disposed onthe lead body 110. These stimulation electrodes may be made using ametal, alloy, conductive oxide, or any other suitable conductivebiocompatible material. Examples of suitable materials include, but arenot limited to, platinum, platinum iridium alloy, iridium, titanium, ortungsten. Preferably, the stimulation electrodes are made of a materialthat is biocompatible and does not substantially corrode under expectedoperating conditions in the operating environment for the expectedduration of use.

In at least some embodiments, any of the electrodes can be used as ananode or cathode and carry anodic or cathodic current. In someinstances, an electrode might be an anode for a period of time and acathode for a period of time. In other embodiments, the identity of aparticular electrode or electrodes as an anode or cathode might befixed.

Stimulation electrodes in the form of ring electrodes 120 may bedisposed on any part of the lead body 110, usually near a distal end ofthe lead. FIG. 1 illustrates a portion of a lead having two ringelectrodes. Any number of ring electrodes, or even a single ringelectrode, may be disposed along the length of the lead body 110. Forexample, the lead body may have one ring electrode, two ring electrodes,three ring electrodes or four ring electrodes. In some embodiments, thelead will have five, six, seven or eight ring electrodes. It will beunderstood that any number of ring electrodes may be disposed along thelength of the lead body 110. In some embodiments, the ring electrodes120 are substantially cylindrical and wrap around the entirecircumference of the lead body 110. In some embodiments, the outerdiameter of the ring electrodes 120 is substantially equal to the outerdiameter of the lead body 110. The width of ring electrodes 120 may varyaccording to the desired treatment and the location of the targetneurons. In some embodiments the width of the ring electrode 120 is lessthan or equal to the diameter of the ring electrode 120. In otherembodiments, the width of the ring electrode 120 is greater than thediameter of the ring electrode 120.

Deep brain stimulation leads having segmented electrodes provide forsuperior current steering because target structures in deep brainstimulation are not symmetric about the axis of the distal electrodearray. Instead, a target may be located on one side of a plane runningthrough the axis of the lead. Through the use of a radially segmentedelectrode array (RSEA), current steering can be performed along the axisof the lead but also around the circumference of the lead.

The lead contains a plurality of segmented electrodes 130. Any number ofsegmented electrodes 130 may be disposed on the lead body 110. In someembodiments, the segmented electrodes 130 are grouped in sets ofsegmented electrodes, each set disposed around the circumference of thelead at a particular longitudinal position. The lead may have any numberof sets of segmented electrodes. In at least some embodiments, the leadhas one, two, three, four, five, six, seven, or eight sets of segmentedelectrodes. In at least some embodiments, each set of segmentedelectrodes contains the same number of segmented electrodes 130. In someembodiments, each set of segmented electrodes contains three segmentedelectrodes 130. In at least some other embodiments, each set ofsegmented electrodes contains two, four, five, six, seven or eightsegmented electrodes. The segmented electrodes 130 may vary in size andshape. In some embodiments, the segmented electrodes 130 are all of thesame size, shape, diameter, width or area or any combination thereof. Insome embodiments, the segmented electrodes of each set (or even allsegmented electrodes) may be identical in size and shape.

Each set of segmented electrodes 130 may be disposed around thecircumference of the lead body 110 to form a substantially cylindricalshape around the lead body 110. The spacing of the segmented electrodes130 around the circumference of the lead body 110 may vary as will bedescribed with reference to FIGS. 7B, 8B and 9B. In at least someembodiments, equal spaces, gaps or cutouts are disposed between eachsegmented electrodes 130 around the circumference of the lead body 110.In other embodiments, the spaces, gaps or cutouts between segmentedelectrodes may differ in size or shape. In other embodiments, thespaces, gaps, or cutouts between segmented electrodes may be uniform fora particular set of segmented electrodes or for all sets of segmentedelectrodes. The segmented electrodes 130 may be positioned in irregularor regular intervals around the lead body 110.

Conductors (not shown) that attach to or from the ring electrodes 120and segmented electrodes 130 also pass through the lead body 110. Theseconductors may pass through the material of the lead or through a lumendefined by the lead. The conductors are presented at a connector forcoupling of the electrodes to a control unit (not shown). In oneembodiment, the stimulation electrodes correspond to wire conductorsthat extend out of the lead body 110 and are then trimmed or ground downflush with the lead surface. The conductors may be coupled to a controlunit to provide stimulation signals, often in the form of pulses, to thestimulation electrodes.

FIG. 2 is a schematic side view of another embodiment of a lead having aplurality of segmented electrodes. As seen in FIG. 2, the plurality ofsegmented electrodes 130 may be arranged in different orientationsrelative to each other. In contrast to FIG. 1, where the two sets ofsegmented electrodes are aligned along the length of the lead body 110,FIG. 2 displays another embodiment in which the two sets of segmentedelectrodes 130 are staggered. In at least some embodiments, the sets ofsegmented electrodes are staggered such that no segmented electrodes arealigned along the length of the lead body 110. In some embodiments, thesegmented electrodes may be staggered so that at least one of thesegmented electrodes is aligned with another segmented electrode of adifferent set, and the other segmented electrodes are not aligned.

Any number of segmented electrodes 130 may be disposed on the lead body110 in any number of sets. FIGS. 1 and 2 illustrate embodimentsincluding two sets of segmented electrodes. These two sets of segmentedelectrodes 130 may be disposed in different configurations. FIG. 3A is aschematic perspective view of a third embodiment of a lead having aplurality of segmented electrodes. The lead body 110 of FIG. 3A has aproximal end and a distal end. As will be appreciated from FIG. 3A, thetwo sets of segmented electrodes 130 are disposed on the distal end ofthe lead body 110, distal to the two ring electrodes 120. FIG. 3B is aschematic perspective view of a fourth embodiment of a lead body 110. InFIG. 3B, the two sets of segmented electrodes 130 are disposed proximalto the two ring electrodes 120. By varying the location of the segmentedelectrodes 130, different coverage of the target neurons may beselected. For example, the electrode arrangement of FIG. 3A may beuseful if the physician anticipates that the neural target will becloser to the distal tip of the lead body 110, while the electrodearrangement of FIG. 3B may be useful if the physician anticipates thatthe neural target will be closer to the proximal end of the lead body110. In at least some embodiments, the ring electrodes 120 alternatewith sets of segmented electrodes 130.

Any combination of ring electrodes 120 and segmented electrodes 130 maybe disposed on the lead. In some embodiments the segmented electrodesare arranged in sets. For example, a lead may include a first ringelectrode 120, two sets of segmented electrodes, each set formed ofthree segmented electrodes 130, and a final ring electrode 120 at theend of the lead. This configuration may simply be referred to as a1-3-3-1 configuration. It may be useful to refer to the electrodes withthis shorthand notation. Thus, the embodiment of FIG. 3A may be referredto as a 1-1-3-3 configuration, while the embodiment of FIG. 3B may bereferred to as a 3-3-1-1 configuration. Other eight electrodeconfigurations include, for example, a 2-2-2-2 configuration, where foursets of segmented electrodes are disposed on the lead, and a 4-4configuration, where two sets of segmented electrodes, each having foursegmented electrodes 130 are disposed on the lead. In some embodiments,the lead will have 16 electrodes. Possible configurations for a16-electrode lead include, but are not limited to 4-4-4-4, 8-8,3-3-3-3-3-1 (and all rearrangements of this configuration), and2-2-2-2-2-2-2-2.

FIG. 4 is a schematic diagram to illustrate radial current steeringalong various electrode levels along the length of a lead. Whileconventional lead configurations with ring electrodes are only able tosteer current along the length of the lead (the z-axis), the segmentedelectrode configuration is capable of steering current in the x-axis,y-axis as well as the z-axis. Thus, the centroid of stimulation may besteered in any direction in the three-dimensional space surrounding thelead body 110. In some embodiments, the radial distance, r, and theangle θ around the circumference of the lead body 110 may be dictated bythe percentage of anodic current (recognizing that stimulationpredominantly occurs near the cathode, although strong anodes may causestimulation as well) introduced to each electrode as will be describedin greater detail below. In at least some embodiments, the configurationof anodes and cathodes along the segmented electrodes 130 allows thecentroid of stimulation to be shifted to a variety of differentlocations along the lead body 110.

As can be appreciated from FIG. 4, the centroid of stimulation can beshifted at each level along the length of the lead. The use of multiplesets of segmented electrodes 130 at different levels along the length ofthe lead allows for three-dimensional current steering. In someembodiments, the sets of segmented electrodes 130 are shiftedcollectively (i.e. the centroid of simulation is similar at each levelalong the length of the lead). In at least some other embodiments, eachset of segmented electrodes 130 is controlled independently. Each set ofsegmented electrodes may contain two, three, four, five, six, seven,eight or more segmented electrodes. It will be understood that differentstimulation profiles may be produced by varying the number of segmentedelectrodes at each level. For example, when each set of segmentedelectrodes includes only two segmented electrodes, uniformly distributedgaps (inability to stimulate selectively) may be formed in thestimulation profile. In some embodiments, at least three segmentedelectrodes 130 are utilized to allow for true 360° selectivity.

As previously indicated, the foregoing configurations may also be usedwhile utilizing recording electrodes. In some embodiments, measurementdevices coupled to the muscles or other tissues stimulated by the targetneurons or a unit responsive to the patient or clinician can be coupledto the control unit or microdrive motor system. The measurement device,user, or clinician can indicate a response by the target muscles orother tissues to the stimulation or recording electrodes to furtheridentify the target neurons and facilitate positioning of thestimulation electrodes. For example, if the target neurons are directedto a muscle experiencing tremors, a measurement device can be used toobserve the muscle and indicate changes in tremor frequency or amplitudein response to stimulation of neurons. Alternatively, the patient orclinician may observe the muscle and provide feedback.

The reliability and durability of the lead will depend heavily on thedesign and method of manufacture. Fabrication techniques discussed belowprovide methods for manufacturing leads that have demonstrated very lowincidents of lead breakage.

In some embodiments, fabrication of a lead begins with the proximal end.FIG. 5 is a perspective view of a portion of a lead 500 havingconductors 540 exposed at the distal end of the lead body 510. Asdescribed above with reference to FIG. 1, the conductors 540 attach toor from pre-electrodes 600 and also pass through the lead body 510.These conductors may pass through the material of the lead or through alumen defined by the lead. In some embodiments, the stimulation orrecording electrodes correspond to wire conductors that extend out ofthe lead body 510 and are then trimmed or ground down flush with thelead surface. The conductors 540 may further be coupled to terminals(not shown). The terminals are typically disposed at the proximal end ofthe one or more lead bodies for connection to corresponding connectorcontacts in connectors disposed on, for example, a control module (or toother devices, such as connector contacts on a lead extension, anoperating room cable, or an adaptor). Furthermore, the control modulemay provide stimulation signals, often in the form of pulses, to thestimulation electrodes. The length of the lead body 510 and theconductors 540 exposed at the distal end may vary as required for thefinal product configuration.

In some embodiments, fabrication of a radially segmented electrode arraybegins with a pre-electrode, from which segmented electrodes are formed.FIG. 6 is a schematic cross-sectional view of a pre-electrode 600. Insome embodiments, as seen in FIG. 6, the pre-electrode 600 has twothin-walled portions 610 separated by two thick-walled portions 620. Thethin-walled portions 610 and thick-walled portions 620 may be formed bycreating an inner diameter 630 and an outer diameter 640. In someembodiments, the outer diameter 640 is isodiametric, but the innerdiameter 630 is not isodiametric. Instead, the inner diameter 630 mayhave an irregular diameter including, for example, keyed portions 635where the inner diameter is larger than the remaining portions or whereportions of the pre-electrode 600 have been removed or are unformed. Thekeyed portions 635 may be the result of a sudden change in diameter asseen in FIG. 6 or a more gradual change in diameter.

The resulting thin-walled portions 610 and thick-walled portions 620 mayvary in size. In some embodiments, the thin-walled portions 610 andthick-walled portions 620 are of equal radial size. In at least someother embodiments, the majority of the circumference of thepre-electrode 600 forms the thick-walled portions 620. As seen in FIG.6, in some embodiments, two thick-walled portions and two thin-walledportions are formed. In some embodiments, the thin-walled portions 610are of equal radial size. In some embodiments, the thick-walled portions620 are of equal radial size. It will be understood that in at leastsome other embodiments, one thick-walled portion may be formed largerthan another thick-walled portion.

In some embodiments, the lead body 510 of FIG. 5 includes ablatedsections for receiving the pre-electrodes 600 of FIG. 6. In someembodiments, the ablated sections of the lead body are disposed on thedistal end of the lead body 510, particularly portions of the lead body510 disposed under the pre-electrodes 600. In some embodiments, slots,grit, sand-blasted or roughened regions, or a coating such as titaniumnitride may be added to the pre-electrodes 600, in particular the innerdiameter, to increase adhesion to the lead body 510. Conductors may thenbe coupled to the pre-electrodes 600. In some embodiments, theconductors are welded to the pre-electrodes 600 though it will beunderstood that any suitable method of coupling the pre-electrodes tothe conductors may be utilized, such as laser welding, resistancewelding, conductive epoxy, and the like. As seen in FIG. 6, thepre-electrode 600 may include slotted positions 650 for positioning ofthe conductor and welding. In some embodiments, a plurality of slottedpositions may be disposed on the pre-electrode 600, so that each portionof the pre-electrode 600 is connected to a conductor. In at least someembodiments, as seen in FIG. 6, the slotted positions 650 are disposedon opposite sides of the pre-electrode 600.

In some embodiments, spacers 520 are disposed next to each pre-electrode600 along the length of the lead body 510. The spacers 520 may bedisposed between the pre-electrodes 600 and may have a hollow centerarea such that the spacers 520 can be threaded onto the lead body 510 orcan be used as a part of the lead body 510 to separate the electrodes.The lead 500 may also include an end spacer (not shown). The end spaceris disposed at the distal end of the lead 500. The end spacer may haveany shape, but is preferably rounded at the distal end. The spacers 520and the end spacer can be made of any non-conductive biocompatiblematerial including, for example, silicone, polyurethane, andpolyetheretherketone (PEEK). The spacers 520 help electrically isolatethe pre-electrodes 600. Additionally or alternatively, thepre-electrodes can be disposed over portions of a contiguous,non-conducting lead body 510 with an opening through the lead body 510to allow the conductors 540 to be coupled to the pre-electrodes 600.

In some embodiments, the outer diameter of the pre-electrodes 600 may bethe same as the outer diameter of the spacers. In some otherembodiments, the outer diameter of the pre-electrodes 600 mayalternatively be greater than the outer diameter of the spacers 520 suchthat the pre-electrodes 600 are raised above the spacers 520.Alternatively, the outer diameter of the spacers 520 may be greater thanthe outer diameter of the pre-electrodes 600 such that thepre-electrodes are recessed.

An assembly may be subject to a reflow operation after all the spacers520 and pre-electrodes 600 have been loaded onto the lead body 510 andattached to conductors 540 as necessary. The reflow operation is usefulin attaching the spacers 500 and pre-electrodes 600 to the lead body 510and improves structural integrity of the assembly and leads to improvedreliability.

The lead 500 may then be further processed to remove portions of thepre-electrodes 600. In some embodiments, the lead 500 is centerlessground to remove portions of the outer diameter 640 (e.g. to remove thethin-walled portions 610), although it will be understood that anysuitable method can be used to remove these portions including cutting,skiving or laser ablation. FIG. 7 is a schematic cross-sectional view ofthe pre-electrode 600 of FIG. 6 after the thin-walled portions 610 havebeen removed. As seen in FIG. 7, the result of removing the thin-walledportions is that two segmented electrodes 700 are formed. Thus, thethin-walled portions 610 and thick-walled portions 620 may be arrangedso that any configuration of segmented electrodes 700 is formed aftergrinding. It will be appreciated that the slotted positions 650 can alsobe arranged so that each segmented electrode 700 is connected to aconductor after the grinding process.

FIG. 8 is a schematic cross-sectional view of a pre-electrode 800 havingthree thin-walled portions 810 separated by three thick-walled portions820. The pre-electrode 800 has an inner diameter 830 and an outerdiameter 840. As seen in FIG. 8, the inner diameter has three keyedportions 835. As seen in FIG. 9, the pre-electrode 800 of FIG. 8 is ableto form three segmented electrodes 900 when the thin-walled portionshave been removed using the methods described above. In someembodiments, the three segmented electrodes 900 are of the same size. Inat least some other embodiments, the keyed portions 835 will be arrangedso that segmented electrodes 900 of different sizes are produced afterthe grinding process. Furthermore, the keyed portions may be arranged sothat each segmented electrode includes a slotted position 850 forconnected to a conductor. It will be understood that any number ofsegmented electrodes may be formed in this manner. For example, leadshaving four, five, six, seven, eight, ten, twelve or sixteen radiallyarranged segmented electrodes may be produced using these methods.

In at least some other embodiments, radially segmented electrode arraysare formed starting with a plate. FIG. 10A is a schematic perspectiveview of a plurality of electrodes 1000 coupled to a plate 1010. Theplurality of electrodes 1000 may be coupled to the plate 1010 using anysuitable method, such as resistance welding, laser welding, adhesive orthe like. In some embodiments, the plate 1010 is an iron plate, althoughany suitable metal may be used that is capable of acting as a supportstructure and being removed by any of the processes described above(e.g., by a selective etching process.)

The plurality of electrodes 1000 may be disposed on the plate 1010 inany desired arrangement. For example, in some embodiments, the pluralityof electrodes 1000 are divided into equally spaced rows on the plate1010. Each row may include the same number or a different number ofelectrodes. In some embodiments, the rows include a different number ofelectrodes. The rows may also be offset from one another, such thatelectrodes are not longitudinally aligned. The spacing betweenelectrodes may also vary within rows or between rows. In at least someother embodiments, the plurality of electrodes 1000 are disposed on theplate 1010 in a circular arrangement, a diagonal arrangement, or in anyother desired pattern.

Conductors (not shown) are then joined to the plurality of electrodes1000 by welding or other techniques. In some embodiments, eachindividual electrode is connected to a separate and distinct conductor.In at least some other embodiments, multiple electrodes are connected tothe same conductor.

In some embodiments, the plate 1010 is then formed into a cylinder. Insome embodiments, in order to create a cylinder, a mandrel is placedalong the midline of the plate 1010 and inserted into the central lumenof a lead body of the proximal end sub-assembly. The plate 1010 may thenbe drawn through a die, or a series of dies to form the desiredcylindrical shape. The cylinder may be formed so that conductors, stillattached to the plurality of electrodes 1000, extend through the centrallumen of the cylinder. FIG. 10B is a schematic perspective view of theplurality of electrodes 1000 coupled a plate 1010 after the plate 1010has been formed into a cylinder 1020.

The newly-formed cylinder 1020 includes a hollow central lumen with theconductors extending through the lumen. The central lumen of thecylinder 1020 may be filled with an insulative or polymeric material tocreate a lead body 1030. As previously indicated, suitable polymericmaterials include, but are not limited to, silicone, polyurethane, andpolyethylene. FIG. 10C is a schematic perspective view of the cylinderof FIG. 10B after its lumen has been filled with an insulative materialto create a lead assembly 1040. In some embodiments, a liquid siliconerubber is injected into the cylinder 1020 to form a lead body 1030.

After the cylinder 1020 has been injected with an insulative material toform a lead assembly 1040, the lead assembly 1040 may then be subjectedto a series of steps to cure it. The plate 1010 is then removed from thelead assembly 1040 to expose the plurality of electrodes 1000. In someembodiments, the lead assembly 1040 is placed in an acid bath todissolve the plate 1010. Alternatively, any suitable technique may beused to remove the plate 1010 from the lead assembly 1040. FIG. 10D is aschematic perspective view of the cylinder of FIG. 10C after the plate1010 has been removed. The lead assembly 1040 includes a plurality ofelectrodes 1000 in a radial arrangement corresponding to the arrangementchosen for welding the plurality of electrodes 1000 to the plate 1010.

It will be understood that in some embodiments, a lead is formed using avariety of materials. For example, the material injected into thecylinder 1020 need not be the same material used throughout the rest ofthe lead. The choice of materials for lead construction can depend on avariety of factors including, for example, biocompatibility, mechanicalproperties (e.g., flexibility, tensile strength, tear strength, andelongation), biostability, handling properties, ease of manufacture,cost, production time, and the like. Thus, leads can be produced usingdifferent materials along different parts of the lead. For example, adistal end can be made of one material, for example, silicone orpolyurethane, and the proximal end of the lead can be made using anothermaterial, for example, polyurethane or PEEK. As one example, siliconemay be selected for the distal end of the lead because it is a moreflexible material. Polyurethane may be selected for the proximal endbecause it is stiffer and provides better stiffness that improvesinsertion into a control module (e.g., an implantable pulse generator)or a lead connector. In these leads, the two portions of the lead madeof different materials couple together at a transition site. Thetransition site can generally be any suitable site along the length ofthe lead between the proximal and distal ends. Transition sites can alsooccur even when the two portions of the lead are made of the samematerial and later joined together. It will be recognized that thetransition site can be positioned at any point along the lead and that alead may contain more than one transition site.

In some embodiments, a sleeve over the transition site is used to couplethe two portions of the lead together. A sleeve, however, may increasethe diameter of the lead at the transition site which may beundesirable, particularly because a larger diameter introducer may beneeded to accommodate the larger diameter of the lead at the transitionsite.

In at least some other embodiments, instead of a sleeve, the twoportions of the lead at the transition site can be coupled by modifyingthe ends of the portions to form a connecting arrangement. The leadincludes a first lead portion, for example, the portion injected intothe cylinder 1020, made of a first material and a second lead portionmade of second material. For example, the first material can be siliconeand the second material can be a polyurethane, or vice versa. It will berecognized that the first lead portion can be either the distal orproximal portion of the lead and that the second lead portion is thenthe proximal or distal portion of the lead, respectively.

FIG. 11D is a schematic perspective view of one embodiment of anelectrode 1100 that can be molded into a carrier using liquid injectionmolding. This process will be described in greater detail with referenceto FIGS. 11A-11C. As seen in FIG. 11A, the electrodes 1100 may be placedin the desired array arrangement by positioning the electrodes 1100 in acarrier mold 1120. In some embodiments, the electrodes 1100 are curvedas seen in FIGS. 11A-D. In at least some other embodiments, theelectrodes 1100 are flat when placed in the carrier mold, and laterformed into the desired shape. Suitable materials for the carrier mold1120 include, but are not limited to, metal, polymers (includingplastics), composite materials, and the like. Preferably, the carriermold 1120 is made of a durable material that allows the carrier mold1120 to be reused. In some embodiments, the carrier mold 1120 is curvedor cylindrical. The electrodes 1100 may be disposed in the carrier moldin any suitable arrangement. The electrodes 1100 may, for example, beplaced in two, three, or four columns within the carrier mold 1120 andeach column may contain any number of electrodes. Because a carrier maybe wrapped around a mandrel, columns of electrodes 1100 disposed withina carrier mold 1120 may coincide with a circumferential electrodearrangement as seen in FIG. 1.

The carrier mold 1120 may include electrode positioning features 1125,e.g., indentations or depressions in the carrier mold 1120, that aredisposed in the desired array arrangement. The electrode positioningfeatures 1125 aid positioning of the electrodes 1100 in thepre-determined arrangement. For example, the electrodes 1100 may beplaced in a carrier mold 1120 that has indentations in the bottom of themold that accommodate the shape of the electrodes 1100 and keep theelectrodes 1100 in position during the process of manufacturing thecarrier. The electrodes 1100 may be concave and the carrier mold 1120may have indentations that accommodate the concave shape of theelectrodes 1100. Preferably, at least a portion of the side surface ofthe electrodes 1100 remains exposed within the carrier mold 1120.

As can be appreciated from FIG. 11B, after the electrodes 1100 arepositioned in the carrier mold 1120, a carrier mold cover 1130 may beplaced over the electrodes 1100 and the carrier mold 1120. Suitablematerials for the carrier mold cover 1130 include, but are not limitedto, metal, polymers (including plastics), composite materials, and thelike. Preferably, the carrier mold cover 1130 is made of a durablematerial, such as metal, that allows the carrier mold cover 1130 to bereused.

FIG. 11C is a schematic cross-sectional view of the assembly of FIG. 11Bafter a carrier 1140 has been molded around the array of electrodes1110. The carrier 1140 can be made of any biocompatible materialincluding, for example, silicone, polyurethane, polyetheretherketone(PEEK), epoxy, and the like.

The carrier 1140 may be formed by any process including, for example,molding (including injection molding), casting, and the like. In someembodiments, the carrier 1140 is formed by injection molding. After thecarrier 1140 is molded around the electrodes 1100, conductors (notshown) are joined to the electrodes 1100 positioned in the carrier 1140.Optionally, the intermediate assembly, which includes the completedcarrier and the array of electrodes 1100, can be removed from thecarrier mold 1120 before the conductors are coupled to the electrodes1100. The carrier 1140 with welded cables is then wrapped around amandrel to create a substantially cylindrical shape and placed into anovermold. The assembly is then overmolded forming a radially segmentedelectrode array.

The above specification, examples and data provide a description of themanufacture and use of the composition of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention also resides in theclaims hereinafter appended.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A pre-electrode, comprising: at least twothin-walled portions; and at least two thick-walled portions, whereinthe at least two thick-walled portions separate the at least twothin-walled portions; wherein the pre-electrode is formed in the shapeof a ring having an isodiametric outer diameter and a non-isodiametricinner diameter, wherein the at least two thin-walled portions and the atleast two thick-walled portions are conductive.
 2. The pre-electrode ofclaim 1, wherein the at least two thin-walled portions of thepre-electrode are equally spaced around a circumference of thepre-electrode.
 3. The pre-electrode of claim 1, wherein the at least twothick-walled portions and the at least two thin-walled portions have asame outer diameter.
 4. The pre-electrode of claim 1, wherein an innerdiameter of the at least two thick-walled portions is smaller than aninner diameter of the at least two thin-walled portions.
 5. Thepre-electrode of claim 1, wherein the at least two thin-walled portionsis at least three thin-walled portions and the at least two thick-walledportions is at least three thick-walled portions.
 6. The pre-electrodeof claim 1, wherein each of the at least two thick-walled portions has asame circumferential length along the circumference of thepre-electrode.
 7. The pre-electrode of claim 6, wherein each of the atleast two thin-walled portions has a same circumferential length alongthe circumference of the pre-electrode.
 8. The pre-electrode of claim 7,wherein the circumferential length of the at least two thick-walledportions is greater than the circumferential length of the at least twothin-walled portions.
 9. The pre-electrode of claim 1, furthercomprising marks for coupling with a lead body.
 10. The pre-electrode ofclaim 1, further comprising at least two conductors, wherein each of theat least two conductors is coupled to one of the thick-walled portions.11. A pre-electrode, comprising: at least two thin-walled portions; andat least two thick-walled portions, wherein the at least twothick-walled portions separate the at least two thin-walled portions;wherein the at least two thick-walled portions and the at least twothin-walled portions have a same outer diameter and an inner diameter ofthe at least two thick-walled portions is smaller than an inner diameterof the at least two thin-walled portions, wherein the at least twothin-walled portions and the at least two thick-walled portions areconductive.
 12. The pre-electrode of claim 11, wherein the at least twothin-walled portions of the pre-electrode are equally spaced around acircumference of the pre-electrode.
 13. The pre-electrode of claim 11,wherein the at least two thin-walled portions is at least threethin-walled portions and the at least two thick-walled portions is atleast three thick-walled portions.
 14. The pre-electrode of claim 11,wherein each of the at least two thick-walled portions has a samecircumferential length along the circumference of the pre-electrode. 15.The pre-electrode of claim 14, wherein each of the at least twothin-walled portions has a same circumferential length along thecircumference of the pre-electrode.
 16. The pre-electrode of claim 15,wherein the circumferential length of the at least two thick-walledportions is greater than the circumferential length of the at least twothin-walled portions.
 17. A pre-electrode, comprising: at least twothin-walled portions; and at least two thick-walled portions, whereinthe at least two thick-walled portions alternate with the at least twothin-walled portions around a circumference of the pre-electrode,wherein the pre-electrode has an isodiametric outer diameter and anon-isodiametric inner diameter and the at least two thin-walledportions and the at least two thick-walled portions are conductive. 18.The pre-electrode of claim 17, wherein the at least two thin-walledportions of the pre-electrode are equally spaced around a circumferenceof the pre-electrode.
 19. The pre-electrode of claim 17, wherein the atleast two thin-walled portions is at least three thin-walled portionsand the at least two thick-walled portions is at least threethick-walled portions.
 20. The pre-electrode of claim 17, wherein eachof the at least two thick-walled portions has a same circumferentiallength along the circumference of the pre-electrode, each of the atleast two thin-walled portions has a same circumferential length alongthe circumference of the pre-electrode, and the circumferential lengthof the at least two thick-walled portions is greater than thecircumferential length of the at least two thin-walled portions.